Just got back from a heating cycle with the gears. Drove 20 min at varying speeds from 30-55mph.

Came home and parked the Jeep. Crawled under the Jeep to do some visual inspections. First thing I noticed was the rear diff is VERY HOT. It is my understanding that this is normal so I'm not too worried about it.

Is the rear differential too hot to touch ? Mine was warm when I got home , but not hot .

I installed Synergy ball joints in mine last spring before we headed West and they have been fine so far . My stock spicers seemed ok at 75K but once I had the knuckle stripped a lot play became more evident . The Synergy's arent supposed to have any plastic in them like my stock ones did and that was the main selling point for me .

Is the rear differential too hot to touch ? Mine was warm when I got home , but not hot .

I installed Synergy ball joints in mine last spring before we headed West and they have been fine so far . My stock spicers seemed ok at 75K but once I had the knuckle stripped a lot play became more evident . The Synergy's arent supposed to have any plastic in them like my stock ones did and that was the main selling point for me .

I could put my hand on it for about 2-3 seconds tops. It was pretty hot. The front diff was warm and I could keep my hand there as long as I wanted. I searched around here on the forums and most people said it was normal.

Do the Spicer HD's have any plastic in them? I can get the Spicers for $100 for all 4. The Synergy's are $250 for all 4. If the Spicers last 75k miles…I don't see the point in buying the Synergy's. It's likely these Rubicon axles have about 2 seasons left on them before they are gone.

I dont know the answer about the hd spicers , but the stockers do have plastic in them . $250 shipped from Northridge was the best price I could find for the Synergy's . I cant say that they are worth it for most people, but they were worth it to me as I didnt want to mess with that job again any time soon .

I dont know the answer about the hd spicers , but the stockers do have plastic in them . $250 shipped from Northridge was the best price I could find for the Synergy's . I cant say that they are worth it for most people, but they were worth it to me as I didnt want to mess with that job again any time soon .

I'm wondering if the Spicers have any plastic in them or not. I know the Synergy's don't which is very nice to know considering the amount of abuse the ball joints take.